1. Field of the Invention
This invention relates to knock detection for vehicle engines.
2. Prior Art
Spark knock in a vehicle mounted internal combustion engine produces a vibration or characteristic pinging sound.
Various knock sensors for detecting knock are known. Typically, upon detection of knock, the spark is retarded to eliminate knock. Known knock sensors include various accelerometers wherein a mass vibrates in response to engine vibration. This vibration is sensed electrically to produce an output signal. For example, a piezoelectric crystal mounted on a disc free to vibrate can produce an output electrical signal.
A common shortcoming in such systems is that they only correct knock after it occurs. It would be advantageous to be able to anticipate the occurrence of knock and prevent it from happening. Further, conventional knock sensors and detector systems usually exhibit relatively low signal to noise ratios. This requires the use of low pass filtering or other signal averaging techniques to reduce the effects of noise. The resulting control system time delay usually permits several knocks to be heard whenever the throttle is rapidly opened. This transient knock disappears as the control system responds by retarding the spark. These are some of the problems this invention overcomes.